1. Field of the Invention
This invention relates to semiconductor varistors and a method of making the same.
2. Description of the Prior Art
Varistors are nonlinear resistive elements commonly used to protect electrical circuits or electrical apparatus from high voltage surges. In particular, it is often desirable to protect power lines from high voltage surges to protect the transformers, insulators and electrical equipment associated therewith. One type of prior art varistor embodies a polycrystalline material such, for example, as a zinc oxide-bismuth oxide combination. However, it has been discovered that materials such as this combination experience an increase in leakage current with the passage of time. One could use a plurality of several connected back-to-back Zener diodes but the economics of such a system is prohibited. Additionally, each electrical connection is a potential source of failure particularly if a sound electrical connection has not resulted from the joining operation.
An object of this invention is to provide a new and improved semiconductor varistor which overcomes the deficiencies of the prior art devices.
Another object of this invention is to provide a new and improved semiconductor varistor having a lamellar structure including spaced regions of recrystallized substrate material.
Another object of this invention is to provide a new and improved semiconductor varistor having a lamellar structure including spaced regions of recrystallized substrate material having a substantially uniform dopant impurity concentration through the regions.
Other objects of this invention will, in part, be obvious and will, in part, appear hereinafter.